Use of (C1 -C5) alkyl esters of aliphatic (C8 -C22) monocarboxylic acids for removing fat, inks and the like from printing machines

ABSTRACT

Use of (C 1  -C 5 ) alkyl esters of aliphatic (C 8  -C 22 ) monocarboxylic acids for removing fat, inks and the like from printing apparatus, in particular from offset printing machines, and a cleaning agent for this, containing as its main component a (C 1  -C 5 ) alkyl ester of an aliphatic (C 8  -C 22 ) monocarboxylic acid or a mixture of such esters. 
     The most suitable esters are methyl, ethyl or isopropyl esters or mixtures thereof, and particularly expedient is an ester mixture obtained by interesterification of an oleic acid containing oil or by esterification of an acid mixture having a corresponding composition. 
     The ester or ester mixture may be admixed with up to 50% by weight of vegetable oil. 
     Further, the ester or ester mixture or the mixture thereof with vegetable oil may be emulgated in water in such amount that the water phase comprises up to 50%, preferably 25-35% by weight of the emulsion using an emulsifier in an amount of 1-10%, preferably 3-5% by weight of the emulsion. In that case it is convenient to further add a corrosion inhibitor in an amount of up to 2%, preferably 0.5-1% by weight of the emulsion. 
     These esters and mixtures are low viscosity substances which are excellent and quickly acting solvents for inks, etc. They are moreover biologically degradable, non-toxic and have a low vapor pressure so that they do not involve any risk for the environment.

The invention concerns a special use of (C₁ -C₅) alkyl esters ofaliphatic (C₈ -C₂₂) monocarboxylic acids for removing inks and the likefrom printing machines, in particular from offset printing machines. Theinvention also concerns an agent and a method for removing fat, inks andthe like from printing machines, in particular from offset printingmachines.

In the past white spirit, optionally in mixture with chlorinatedhydrocarbons and/or with surfactants and optionally additionallydispersed in water, was generally used for cleaning printing machines offat, inks and the like.

The cleaning was effected by spraying the cleaning agent onto theuppermost inking roller. With the machine running, the cleaning agentwas dispersed downwards over the other rollers and was removed by meansof a washing doctor clamped to the bottom roller. After a couple ofsprayings with the cleaning agent the rollers were clean. The cleaningoperation was ended by spraying the rollers with water, and then themachine was ready for printing again. In special cases at was necessaryto wipe the rollers with a clean cloth. Now and then it was alsonecessary to wipe the printing plate and the rubber blanket with a clothmoistened with the cleaning agent.

Owing to the harmful effects on the environment of using white spirit,kerosine or other mineral oil products it has been attempted to useother substances having corresponding properties. E.g., in the graphicindustry it has been attempted to use liquid fatty oils, e.g. soy beanoil, for cleaning offset printing machines of ink. Such cleaning iseffected in the same way as described above. However, strong clothrubbing on the rollers is also necessary for the oil to be able todissolve all the ink, and the process must often be repeated severaltimes to obtain clean rollers. This is caused partly by the highviscosity of the oil, partly by the low dissolution rate.

Methylester of fatty acids have been used for aqueous cleaning purposes.U.S. Pat. No. 4,180,472 discloses compositions and methods for removingoily soils from fabrics in an aqueous washing process. The compositionsconsist of 20-97% alkanes or fatty acid esters and 3-30% emulsifiers.The concentration of the alkanes or fatty acid esters is from about 0.1to about 3% in the aqueous washing medium.

British Patent No. 1 240 769 discloses an aqueous composition suitablefor cleaning metal, glass and painted surfaces. The composition containsinorganic or organic acids, for instance 50% concentrated phosphoricacid, cationic emulsifiers and small amounts of oily substances, forinstance fatty acid esters, which are added to increase the viscosity ofthe composition and increase the adhesive properties. The compositionmay be diluted with water before application in a ratio of from 1:2 to1:10 by volume.

Japanese Patent No. 81 035 716-B discloses a non-aqueous composition andmethod for removing scales of soap on the inside wall of heatexchangers. The composition consists of a mixture of fatty acids andtheir methyl esters, and the cleaning is performed at 100°-130° C.

It has surprisingly been found that all the above-mentioned drawbacks inthe cleaning of printing machines, in particular offset printingmachines are obviated by using, according to the invention, a (C₁ -C₅)alkyl ester or an aliphatic (C₈ -C₂₂) monocarboxylic acid or a mixtureof such esters. With such agent the cleaning can be performed in thesame way as described above using cleaning agents based on organicsolvents.

Generally, the best results are obtained by using the ester or estermixture alone.

In certain cases cleaning of offset printing machines may cause a weakfilm to be formed on the "Rilsan"® rollers so that some ink istransferred to the wetting device and ink the filt rollers. This may becounteracted by dissolving a small amount, up to 10% by weight, of oneor more surfactants in the ester or ester mixture.

Thus it is preferred according to the invention to use the ester orester mixture containing up to 10%, preferably 0.5-2% by weight ofsurfactant.

It is also possible according to the invention to use a mixture of theester or ester mixture with up to 50% by weight of vegetable oil, saidmixture optionally containing up to 10% by weight of surfactant.

The above agents may further, according to the invention, be emulgatedin water in such amount that the water phase comprises up to 50%,preferably 25-35% by weight of the emulsion, using an emulsifier in anamount of 1-10%, preferably 3-5% by weight of the emulsion. In that caseit is convenient to further add a corrosion inhibitor in an amount of upto 2%, preferably 0.5-1% by weight of the emulsion.

Oil-in-water emulsions of the (C₁ -C₅) alkyl esters of aliphatic (C₈-C₂₂) monocarboxylic acids generally have a much higher viscosity thanthe neat esters. However, the emulsions are readily dispersed on theprinting machines, and they are removed without difficulty by rinsingwith water after the cleaning operation.

Thus, in a general sense, use according to the invention may be made ofa mixture comprising 50-100% by weight of a (C₁ -C₅) alkyl ester of analiphatic (C₈ -C₂₂) monocarboxylic acid or mixture of such esters, 0-50%by weight of vegetable oil and 0-10%, preferably 0.5-2% by weight ofsurfactant, said mixture being optionally emulgated in water in suchamount that the water phase comprises up to 50%, preferably 25-35% byweight of the emulsion, using an emulsifier in an amount of 1-10 %,preferably 3-5% by weight of the emulsion and optionally adding acorrosion inhibitor in an amount of up to 2%, preferably 0.5-1% byweight of the emulsion.

Particularly suited for use according to the invention are esters whichare liquid at room temperature.

The most suitable esters for use according to the invention are methyl,ethyl or isopropyl esters or mixtures thereof, and particularly usefulis the methyl ester.

According to the invention, the fatty acid esters may be saturated, butparticularly useful are ester mixtures comprising esters of unsaturatedfatty acids, such as oleic, linoleic, linolenic and erucic acid.

Esters containing unsaturated fatty acids have a particularly lowmelting point, but to obtain improved stability against oxidationpartially hydrogenated esters may be used, the content ofpolyunsaturated fatty acids having been reduced by partial hydrogenationof the esters or of the fatty acids or fats used in the production ofthe esters.

Also esters of ricinoleic acid may be used according to the invention.

The present esters can be produced in a known manner by esterificationof a suitable (C₈ -C₂₂) monocarboxylic acid or a mixture of such acidswith a (C₁ -C₅) alcohol. They can also be produced in a known manner byinteresterification of a suitable fat (triglyceride) with a (C₁ -C₅)alcohol, optionally after preceding fractionation of the fat or byfractionation of the ester mixture to provide mixtures havingparticularly desirable properties.

It is particularly expedient, both with respect to composition andprice, to use an ester mixture obtained by interesterification of anoleic acid containing oil or by esterification of a fatty acid mixturehaving a corresponding composition. The oleic acid containing oil mayadvantageously be selected from soy bean oil, rapeseed oil, olive oil,sunflower oil, cottonseed oil, palm oil, palm kernel oil, and coconutoil.

When liquid, these esters are low viscosity substances which, aftercleaning of the printing machines, can easily be removed again withoutleaving an oil film. They are likewise excellent and quickly actingsolvents for inks, etc.

The esters are biologically degradable, and they are not toxic. Thus,the methyl esters have an LD₅₀ greater than 10 g/kg body weight forrats. They have such a low vapour pressure at room temperature that thevapours do not have any discomforting effect when inhaled.

The esters moreover have such a high flash point that they can betransported, stored and used without fire danger problems.

The vegetable oils which can be used in admixture with the (C₁ -C₅)alkyl esters of aliphatic (C₈ -C₂₂) monocarboxylic acids include soybean oil, rapeseed oil, sunflower oil, cottonseed oil and low-meltingfractions of palm oil, palm kernel oil and coconut oil and mixturesthereof. Coconut oil, palm kernel oil and palm oil may be used inamounts of 0-25% by weight. A content of 5-15% by weight of these oilsor mixtures thereof is especially convenient, as higher contentsincrease the viscosity of the agent making it more difficult to removefrom the printing machines after the cleaning operation.

A suitable class of surfactants for use according to the invention is ofthe type of polyglycol ethers of aliphatic (C₈ -C₂₂) alcohols.

A suitable class of emulsifiers for preparing aqueous emulsions for useaccording to the invention is of the type of saturated (C₁₂ -C₂₂) fattyalcohols ethoxylated with 7-14, in particular 9-12, ethoxy groups.

As examples of corrosion inhibitors to be added to the aqueous emulsionsmay be mentioned aliphatic primary amines having 12-18 carbon atoms.

The invention further concerns an agent for removing, inks and the likefrom printing machines, in particular from offset printing machines,which is characterized in that as a main component it comprises a (C₁-C₅) alkyl ester of an aliphatic (C₈ -C₂₂) monocarboxylic acid or amixture of such esters.

More specifically the agent according to the invention consists of amixture comprising 50-100% by weight of a (C₁ -C₅) alkyl ester of analiphatic (C₈ -C₂₂) monocarboxylic acid or mixture of such esters, 0-50%by weight of vegetable oil and 0-10%, preferably 0.5-2% by weight ofsurfactant, said mixture being optionally emulgated in water in suchamount that the water phase comprises up to 50%, preferably 25-35% byweight of the emulsion, using an emulsifier in an amount of 1-10 %,preferably 3-5% by weight of the emulsion and optionally adding acorrosion inhibitor in an amount of up to 2%, preferably 0.5-1% byweight of the emulsion.

As mentioned above the most suitable esters to form all or part of theagent according to the invention are methyl, ethyl or isopropyl estersor mixtures thereof, and particularly expedient are the above mentionedester mixtures obtained from oleic acid containing fats and being liquidat ambient temperature.

The vegetable oils, surfactants, emulsifiers and corrosion inhibitors tobe included in the agent according to the invention are preferably ofthe types discussed above.

The agent according to the invention may advantageously contain 0.05-10%by weight of one or more surfactants. If a surfactant is added to thecleaning agent, it will most generally contain 0.4-2% by weight, andpreferably 1-1.5% by weight of surfactant.

The agent according to the invention may moreover contain variousstabilizers, e.g. preservatives and antioxidants, which might be deemednecessary or desirable.

As an example it may be mentioned that methyl esters of fatty acids fromrapeseed oil have the following physical data:

Vapour pressure: 0.027 Pa at 40° C.

Viscosity: 0.007 Pa.s at 25° C.

Flash point: >150° C.

Cold haze point: <-15° c.

Toxicity, LD₅₀ : >20 g/kg body weight (rats)

With this ester mixture excellent results in the cleaning of an offsetprinting machine of ink have been obtained. The ink could easily bewashed off without leaving any film on the rollers and without anydiscomfort to the operator at all.

In certain cases with a tendency to film formation on the "Rilsan"®roller, this could be avoided completely by addition of 1-1.5% by weightof the surfactant "Dehydol® LT7" (heptaethylene glycol monolaurylether). However, usually this is not necessary to obtain a good functionof the product.

The amount of agent to be used in each cleaning operation varies much,according to which colour shift it is desired to make, and how muchremains on the rollers. An offset printing machine comprises 3-5, inspecial cases 7, inking apparatuses, one per colour used. When using theagent according to the invention ordinarily 150-250 ml is sprayed on theuppermost roller of the inking apparatus, and often one spraying issufficient.

When using a solvent-based cleaning agent normally 300-500 ml is sprayedon the uppermost roller of the inking apparatus, and if necessary, thespraying is repeated.

EXAMPLE

Rapeseed oil methyl ester was used for six months for cleaning aplurality of offset printing machines of the Heidelberg make installedat a technical school.

The inking rollers were cleaned by spraying with the rapeseed oil methylester, and then the ester with dissolved ink residues was removed bymeans of a washing doctor. Any greasy film on the rollers was removed bypouring water on the rollers and removing the water with the washingdoctor.

When rubber blanket cylinder and printing plate were washed, small esterresidues were left now and then, causing tinting tendencies. Theresidues were easily removed by wiping with a cloth, application ofwater with a sponge and finally drying with a dry cloth.

The cleaning process is analogous to the previously used cleaningprocess using agents containing solvents. The amount ofsolvent-containing cleaning agent to be used was approximately twice aslarge, and in spite of exhaust at each machine unpleasant concentrationsof solvent vapours were present in the printing room.

The labour involved by cleaning with rapeseed oil methyl ester wassignificantly reduced. Thus, after printing with black ink cleaning oncewith the ester was sufficient, while the solvent-based cleaning agentsusually neccessitates cleaning two or three times.

COMPARATIVE EXAMPLE

Tests with cleaning of offset printing machines by means of soy bean oilhave been performed. Here too, the atmosphere in the printing room wasimproved, but the colour residues were dissolved so slowly that it wasnecessary to rub the rollers with cloths, and the cleaning often had tobe repeated before the rollers were clean. Even then an oil film remainson the rollers and has to be removed by other means.

I claim:
 1. A method of removing ink from a printing machine whichcomprises cleaning the machine with an agent comprised of 50-100% byweight of (C₁ -C₅) alkyl ester of an aliphatic (C₈ -C₂₂) monocarboxylicacid, 0-50% by weight of vegetable oil and 0-10% by weight ofsurfactant.
 2. A method of removing ink from a printing machine whichcomprises cleaning the machine with an emulsion comprised of the agentof claim 1 emulsified in water in such amount that the water phasecomprises up to 50% by weight of the emulsion, and an emulsifier in anamount of 1-10% by weight of emulsion.
 3. A method of removing ink froma printing machine which comprises cleaning the machine with the agentof claim 1, wherein the alkyl ester is a mixture of alkyl esters.
 4. Amethod of removing ink from a printing machine which comprises cleaningthe machine with the emulsion of claim 2, wherein the emulsion containsa corrosion inhibitor in an amount of up to 2% by weight of theemulsion.
 5. A method of removing ink from a printing machine whichcomprises cleaning the machine with the emulsion of claim 2, wherein thewater comprises 25-35% by weight of the emulsion.
 6. A method ofremoving ink from a printing machine which comprises cleaning themachine with the emulsion of claim 5, wherein the emulsifier comprises3-5% by weight of the emulsion.
 7. A method of removing ink from aprinting machine which comprises cleaning the machine with the agent ofclaim 3, wherein the ester mixture has been obtained by esterificationof an oleic acid containing oil.
 8. A method of removing ink from aprinting machine which comprises cleaning the machine with the agent ofclaim 1, wherein the agent contains a vegetable oil which is alow-melting fraction of palm oil, palm kernel oil, coconut oil ormixtures thereof.
 9. A method of removing ink from a printing machinewhich comprises cleaning the machine with the agent of claim 1, whereinthe vegetable oil is palm oil, palm kernel oil, coconut oil or a mixturethereof in an amount of 5-15% by weight of the agent.
 10. A method ofremoving ink from a printing machine which comprises cleaning themachine with emulsion of claim 4, wherein the corrosion inhibitorcomprises an aliphatic primary amine having 12-18 carbon atoms.
 11. Amethod according to claim 1 wherein the cleaning agent is sprayed ontothe uppermost roller of such printing machine, running the machine todisperse the agent downwards over other rollers and removing the agentwith dissolved ink by means of a washing doctor clamped to a bottomroller.
 12. A method according to claim 2 wherein the emulsion issprayed onto an uppermost roller of such printing machine, running themachine to disperse the agent downwards over other rollers and removingthe agent with dissolved ink by means of a washing doctor clamped to abottom roller.
 13. A method for removing inks from a printing machinewhich comprises cleaning the machine with an agent comprising at leastone (C₁ -C₅) alkyl ester of an aliphatic (C₈ -C₂₂) monocarboxylic acid.14. The method of claim 3, wherein the mixture of alkyl esters isobtained by interesterification of an oil selected from the groupconsisting of soybean oil, rapeseed oil, olive oil, sunflower oil,cottonseed oil, palm oil, palm kernel oil and coconut oil, with a (C₁-C₅) alcohol.